Urine paraquat test being used for diquat

The addition of sodium bicarbonate and sodium dithionite to urine specimens containing decreasing concentrations of diquat shows characteristic color changes. This picture was taken immediately after the addition of dithionite to one of three sets of specimens. Set C is pictured here; similar results in dose-dependent color change were noted with the other sets. Each number represents decreasing concentrations of diquat or control as follows: 1—urine only, 2—730 mg/L, 3—365 mg/L, 4—219 mg/L, 5—73 mg/L, 6—51.1 mg/L, 7—36.5 mg/L, 8—21.9 mg/L, 9— 7.3 mg/L, 10—3.65 mg/L, 11—0.73 mg/L, and 12—glyphosate-only herbicide solution.